For a small African fish species, a colorful dominant male does better in life, winning access to food and females. New research by Stanford biologists suggests that this lucky outcome is regulated at a genetic level, by turning genes on and off.

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Fernald studies Astatotilapia burtoni, one of the hundreds of cichlid fish species inhabiting Lake Tanganyika in eastern Africa, because of the unique ways they have evolved over time. For male A. burtoni, dominance is everything. They battle frequently for territory, with the victor winning access to the two most important resources — food and females.

Sporting bright rainbow-colored scales, high-ranking males aggressively defend their foraging grounds and lure females into their territory to dine on decaying matter on the lakebed. In contrast, the low-ranking males, which are dull grey in color, comprise 80 percent of the population but cannot reproduce and must swim with the females to get access to food.

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But some social mobility is possible. Because the flashy dominant males are more vulnerable to predation, whenever a boss fish disappears, a major battle ensues as non-dominant males fight to take over the vacant territory. The winner then ascends to dominant status resulting in an astonishing series of physiological changes, including rewiring of parts of the brain as previously reported by Fernald’s group.

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“We could see the behavioral change in a matter of minutes, as one animal began to dominate the other,” Fernald said. “Videos of these confrontations showed that the fish injected with the methylating agent were much more likely to be the winners, while those receiving the methylation suppressor typically lost the fight for dominance. More.

But while this is certainly a “dominance” struggle, is it correct to call it a struggle over “social status”? The concept of social status presupposes not only a society but a relationship to that society consciously recognized by most actors within it. It is not only the behaviour, but also the consciousness—evident in human affairs, as people strive for social status, even from something as apparently abstract as area codes and zip codes. Purely virtual territory.

Shortly, I (O’Leary for News) will be writing about animals’ sense of self—the “minimal self” as Vincent Torley puts it. Should be fun.

Here’s the abstract: Social status hierarchies are ubiquitous in vertebrate social systems, including humans. It is well known that social rank can influence quality of life dramatically among members of social groups. For example, high-ranking individuals have greater access to resources, including food and mating prerogatives that, in turn, have a positive impact on their reproductive success and health. In contrast low ranking individuals typically have limited reproductive success and may experience lasting social and physiological costs. Ultimately, social rank and behavior are regulated by changes in gene expression. However, little is known about mechanisms that transduce social cues into transcriptional changes. Since social behavior is a dynamic process, we hypothesized that a molecular mechanism such as DNA methylation might play a role these changes. To test this hypothesis, we used an African cichlid fish, Astatotilapia burtoni, in which social rank dictates reproductive access. We show that manipulating global DNA methylation state strongly biases the outcomes of social encounters. Injecting DNA methylating and de-methylating agents in low status animals competing for status, we found that animals with chemically increased methylation states were statistically highly likely to ascend in rank. In contrast, those with inhibited methylation processes and thus lower methylation levels were statistically highly unlikely to ascend in rank. This suggests that among its many roles, DNA methylation may be linked to social status and more generally to social behavior. (paywall)

8 Responses to Social status? In fish?

“But while this is certainly a “dominance” struggle, is it correct to call it a struggle over “social status”? The concept of social status presupposes not only a society but a relationship to that society consciously recognized by most actors within it. “

The term “social status” is commonly used to define the interactions and relationships amongst animals on a group. Not just those common amongst humans. All biologists understand what is meant by this.

Clown fish display a similar but inverse social structure. All are born male. Only the largest and aggressive will become female.

Jonas Crump at 2, thanks for the clarification It seems like a misuse of the term. “All biologists understand what is meant by this” because it is a short route to claiming that apes are entering the Stone Age.

Come on. A more careful approach would be more specific.

The term is likely correctly used when the animals have a social order (dogs, apes, and birds come to mind). We just don’t know much about whether the fish are conscious of a social order.

News, I keep fish (clowns and others) and there is clearly a social order involved. They show distict behaviours (personalities?). “Social status” is a perfectly appropriate term to use. Any confusion comes from your human-centric perspective, not with how the term was used.

With regard to the idea that apes are entering a Stone Age, I don’t see what your concern over this is. It is my understanding that the term simply refers to the time at which our human anscestors started using tools. If apes are demonstrating the use of tools (I have not done any reading on it, so I can’t say) why would it not be correct to say that they are entering their own version of the Stone Age?

Jonas Crump at 4, thanks re fish info. Insects show a social order too, in a sense, but it is unclear that they have distinct personalities or even can.

The concept of social “status” implies an awareness of such. That, in turn, implies some rudimentary consciousness.

I find the whole thing fascinating but many concepts seem unclear at present. What is included, what excluded?

Doubtless more research will yield clearer definitions.

The main problem with claims re apes “entering the Stone Age” is that 1) It is an age known among humans only in retrospect 2) we have no reason to expect an inevitable progress 3) apes have likely always been doing this stuff but no one noticed.

“The main problem with claims re apes “entering the Stone Age” is that 1) It is an age known among humans only in retrospect.”

True. But isn’t that true about everything we have learned from archaeology and from the fossil record?

“we have no reason to expect an inevitable progress.”

Again, I agree. Change may be inevitable, especially with any learned behaviour. But change does not equate to progress. Progress is an attribute that we ascribe to something. And is subjective.

“3) apes have likely always been doing this stuff but no one noticed.”

You may be correct but, unfortunately, it is a pure guess on your part.

The impression I get, and please correct me if I am wrong (us Torontonians must stick together), is that your objection to terms like “social status” and “stone age” in describing animals is that their use tends to anthroposize (is that a word?) animals. I agree that it may have this tendency, but I don’t know what other terms you could use that would not have a bias, either falsely towards human comparisons, falsely away from them.